Encryption is the process of transforming plaintext using a cipher into ciphertext to make it unreadable to anyone except those possessing the key. Decryption is the process of transforming that ciphertext back into plaintext, using the key.

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What does the cipher-text overhead means?

I have two questions here. What does the cipher-text overhead means? Why we were suggested not to encrypts the plain-text itself instead just encrypts only the key (i.e random number)
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what actually the function for e(g,g)^xy

I doing a project using ABE "Attribute-Based-Encryption" but i didn't understand what actually the function for $e(g,g)^xy$. Just tell what's the calculation need to perform here. I gone through no of ...
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Physical Level Encryption

What types of algorithms that are capable of signing a message are out there that run on a physical level, e.g. lacking the infrastructure of a standard PC, no memory, processor or motherboard in the ...
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How to implement order preserving encryption or order preserving hashing [closed]

Does anybody know any free implementation of either order preserving encryption or order preserving hashing? I've found some codes like CMPH but I need to dynamically add new DATA and that's why most ...
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62 views

How secure is this logarithmic encryption algorithm?

How secure would the following logarithmic encryption algorithm be when tested under the same conditions as high end encryption algorithms (AES, RSA etc...). Note: For smaller text the text will be ...
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44 views

Security of DGHV Encryption

In DGHV Security How to get reliable oracle for least significant bit and then uses binary GCD algorothm that uses reliable oracle to find secret key p.Also what is oracle. Is this a turing ...
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In case M is small is it possible to recover the message

In the plain RSA encryption, suppose $N$ is 1024 bits and the public key $e = 17$. Is it secure to use this setting to encrypt very small message, say $3 \leq m \leq 9$? In other words, is it possible ...
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66 views

Why does AES ciphertext entropy always close to 8?

I have three binary files: 31744 byte length (1), 5712980 byte length (2) and 10806008 byte length (3). The alphabet is all 256 symbols from 00 to ff. I compute the shannon entropy, replacing ...
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58 views

Would a non-deterministic (read: randomized) compression algorithm be crypto-safe?

Would a compression algorithm that randomly shifts stuff around every iteration be TLS/crypto-safe? This randomization would prevent the same byte sequence from appearing twice in a row, thus making ...
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k(k-1)/2: Combinations and the Birthday bound

Disclaimer: I'm new to cryptography. Background: I'm reading Cryptography Engineering by Ferguson, Schneier, and Kohno, where, in Chapter 2, the authors write this: Question: What is $k(k-1)/2$ ...
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How would the opponent defraud this secure communication?

I am new in the cryptography and the information security problems, I try to understand things as much as I can and I know it's really complicated in the beginning. Considering the communication ...
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Is it ok to store the plaintext hash of encrypted data

Is it ok to create and store the hash (unkeyed hash function) of a plaintext before encryption or does it lead to vulnerabilities? If it is ok are there requirements for the used hash function and ...
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Is there a way to create an encrypted email with no third party application

I would like to send and receive emails between group of people. Is there a way to create it with no need to use some other 3rd party application. Is there a way just to transfer files between 2 ...
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How to encrypt incomplete block with RSA as a block cipher?

I have a question about an RSA academic example. If we are using block-RSA with a block-size of 3 and we have this message: "android". It is broken into 'and', 'roi', 'd'. How to encrypt the last ...
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62 views

RSA numerical questions

Let $n$ be the modular arithmetic, $p$ and $q$ the two large primes such that $n=p*q$ and $e$ the public exponent. Here they are two "simple" numerical questions: If $p = 13$ and $q = 17$, what is ...
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Certificate Path Verification of X509 Certificate

I have the trusted root certificate which I am validating using the self signed key. I also have the intermediate certificate, which i am validating using the root certificate. Now when i am ...
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How to deliver an encrypted message to multiple recipients without revealing keys

Let's say I have generated a private and a public key. I create a message and encrypt it with the public key. I deliver this encrypted message and a private key to multiple recipients. Why would I do ...
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99 views

ElGamal scheme attack when one message is known and ciphertexts are intercepted

Let $G$ be a finite cyclic group of order $p$ and let $pk = (g, h=g^a)$ and $sk=(g,a)$ be Bob's ElGamal public/secret key pair in $G$. To encrypt a message $m$, a random number $r$ is selected and a ...
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simple algorithm to encrypt/decrypt a text file

I need to write a first program in one language that saves data in a text file, and write a second program in a second language to decrypt that file. The two languages in question don't include any ...
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Adding a Random component to CBC MAC in order to enlarge the tag space

CBC MAC that is using AES as the underlying block cipher, has tag space of 2^128. If we add a random single block, concatenating it with the tag, and encrypt it again in AES CBC mode, with additional ...
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How to decrypt a '.enc' file that has been encrypted with RSA using a public key? [closed]

While solving a CTF challenge online, I came across a situation where I needed to decrypt a '.enc' file that has been encrypted using someone's public key. The ...
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Is the keystream transmitted with the ciphertext when a stream cipher is used?

When a stream cipher is used and a keystream is generated to be XOR'ed with the plaintext, is the keystream sent with the ciphertext so that the receiver knows how to decrypt it? Or does the ...
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How do you implement a cipher as one lookup table?

I am reading up on whitebox cryptography and have trouble understanding how are ciphers implemented as one lookup table? assuming my plaintext is just 4 bits so the size of my lookup table should be ...
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240 views

Difference between the TLS cipher suites?

TLS_DHE_DSS_AES256_CBC_MAC / TLS_DHE_RSA_AES256_CBC_MAC Hi, I have been studying to learn about various cipher suites and their performances. I gathered that DSS is efficient when compared with RSA. ...
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What is the most light-weight symmetric cipher thats still usefull?

I need a very light encryption scheme which costs almost no performance during encryption (while decryption may be slow). I found 5 algorithms: RC4, DES, LED, PRESENT, and Piccolo. But how do I ...
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why do files downloaded with http and https have the same size?

while working with Encryption mostly cipher text is always larger the plain text, why isn't that the case when downloading a file using https ? even that compression isn't much used anymore because if ...
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Block cipher mode with diffusion on ciphertext

As I understand, diffusion property in AES-CBC ensures that one-bit change in plaintext will yield changes in all following blocks in ciphertext upon encryption. I'm looking for algorithm that will ...
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231 views

Repair AES-128 decrypted file

I decrypted a file which was encrypted with OpenSSL and AES-128 with the wrong password. Before I noticed it was the wrong password I removed the original file. Is there a possibility to reproduce the ...
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55 views

What is the probability of finding 4 equal bytes? [closed]

Is it $2^{-32}$ or $2^{-24}$ as one byte is assumed to take a given value and the remaining 3 bytes should have the same value?
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Figure out the encryption being used [closed]

There is a web API (for a game) that sends and receives data encrypted in hex format. I'm interested in accessing the api outside of the game client (mobile app). When sending a request with an ...
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240 views

Simple multiplication as an encryption method

There was a time when I wondered about multiplication as an encryption operation. That was when I was thinking in terms of modular multiplication. But how about based around simple multiplication. ...
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364 views

Client-Server application how can data be encrypted so only clients can read it

Requirements We are building a system that connects multiple clients through a restful API. It allows the creation of groups of trusted clients. We need a way to store group shared data encrypted ...
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Counter Mode with a sequence of zeros bits plaintext, is it secure?

I had a quiz last week in computer security course. There was a confusing question that I am still looking for a good and clear answer. First, I know that counter mode with a good block cipher is ...
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RSA generation of private key using public key

In RSA private key generation e*d ≡ 1 mod φ e is public, also n is public. How to prove mathematically, generation of ...
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CPA security of a stateless and deterministic encryption system

Why can no stateless and deterministic encryption system be IND-CPA secure? Is there a formal proof for it?
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RSA signing security

I'm curious about the security of RSA signing with the same public private key pair when the same message is sent multiple times. It's my understanding that once you generate the hash of the message ...
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Automated testing of cipher security for import/export compliance [closed]

What do we know about systems that automatically test and grade cipher security. The application in mind would be for checking for compliance with import/export regulations. I imagine a system that ...
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How to implement the Salsa20 hash function?

I am currently implementing Salsa20 from the specification as an exercise in learning and self-flagellation. I have Sections 1-7 passing the test examples provided. I am now stuck on Section 8, The ...
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what is it called when encrypt('a') + encrypt('a') == encrypt('aa')?

So normally if you do encrypt('a') twice in a row you'll get the same result. But sometimes (as is the case in SSH) this is not desirable. You want encrypt('a') + encrypt('a') == encrypt('aa'). What ...
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What would be the best plain text Cryptography method without the use of a computer? [closed]

What would be the best Cryptography method without the use of a computer? This could be a list of the current options available, that could be used without the use of a computer ...
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Why has SSL v3 not yet been upgraded to a higher version with stronger principles, what are the dependencies and issues to do so?

SSLv3 is almost 18 years old; why has it not been updated to a more advanced version with stronger rules and structure. What have been the issues and dependencies in doing so till now???
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Prepending random data to encrypted file

If random data is prepended to a file encrypted with GNUPG's symmetric encryption, how may an attacker find out if the input file is deliberately corrupted or the passphrase is wrong? If it is not ...
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blowfish ecb with openssl doesn't give the expected result

I do the following via the Linux CLI: ...
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A variant of Shamir secret sharing

Suppose implement the Shamir secret sharing as following: we select a degree $d$ polynomial $P$ with a zero coefficient of 0, and all other coefficents selected randomly from $Z_p$; and to this ...
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What cryptographic paradigm is appropriate for this use case?

This is a very newbie question... I have to quickly implement a solution for our application that works like this... We have a binary executable that is given a configuration file. I need to encrypt ...
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652 views

Decrypting a small Message using RSA with a Private Key [closed]

If I have a private key of (43, 341). What would be the steps I need to take to decrypt a small message using RSA? I have looked ...
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76 views

encrypting data signals using the time variations between two independent coupling functions [closed]

There was a recent article about a new encryption technique that encrypts "using the time variations between two independent coupling functions". What is this technique they are referring to?
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Can you prove the existance of a PRG $G$ s.t. for each even $k$: $G(k)=G(k+1)$?

In one of the exercises in [KL] Book I need to tell whether an encryption scheme is secure under an eavesdropper of only one message. Given a PRG $G: \{0,1\}^n \rightarrow \{0,1\}^{n+1}$. The ...
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ElGamal encryption with private key [closed]

Does the encryption with a private key and decryption with a public key works in ElGamal likewise what is done when we use RSA for sender authentication?
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563 views

WIN LM Password Hashes (using John the ripper) [closed]

In a problem set, we've been asked to use John The Ripper to crack a list of Win LANMAN passwords. They are of the following form: 953A55E36AB85C0B9DA92C18555E42E1:0169295E0A6A6B35B2DD9932D10C1978 ...